Wednesday, May 13, 2015

Species That Don't Get Enough Publicity #11: Mymoorapelta and Gargoyleosaurus

Most dinosaur groups are stereotyped by the first found or
the largest. Stegosaurus is the only stegosaur in the mass media, Tyrannosaurus
the only tyrannosaur, Brontosaurus the only sauropod, etc. I’m sure
Ankylosaurus is the only armored dinosaur known to most people-it’s the last,
it’s the largest, it’s the first to be found, and it was a neighbor to
Tyrannosaurus rex. However, ankylosaurs had existed for almost 100 million
years before Tyrannosaurus. In fact, we’re going to look at two genera dating
back to the time of Brontosaurus in the late Jurassic period, and lived
alongside the giant sauropods and Stegosaurs.They are the first ankylosaurs-the smallest and most primitive known,
but already well-armored and distinctively ankylosaurs.

These animals are Gargoyleosaurus parkpinorum and Mymoorapelta maysi. Mymoorapelta was first
discovered in 1994 and Gargoyleosaurus in 1998- I first remember going the
Denver museum and finding the skeleton being prepared for mounting that year.
It still stands underneath the DMNS’ giant Diplodocus, a contrast of Jurassic
herbivores. Yes, these are both Morrison animals, much rarer than any other
herbivore but some primitive ornithiscians like Othnielosaurus and Drinker. In
a fauna dominated by sauropods, they shuffled in the shadows of the giants, and
found their own niche.

They were both found by Utah paleontologists and Ankylosaur
experts Kenneth Carpenter and James Kirkland, albeit in different sites. Mymoorapelta
was found in the Myatt-Moore quarry (hence the name) on Colorado’s border in
Utah, in rocks belonging to the Brushy Basin member. Meanwhile, Gargoyelosaurus
was discovered in Bone Cabin Quarry (first found by Walter Granger in 1897) in
Wyoming. Geologically, it was in the Salt Wash member, a million years before
the Brushy Basin and with a subtly different fauna. There’s no reason to assume
they never coexisted, but they seem to be connected to different environments.

They’re both connected to the family Polacanthinae, and
we’ll return to that family at a later date. They are the earliest, most basal
family of ankylosaurs, dating from these two genera to the middle Cretaceous
where they are completely replaced by nodosaurs and ankylosaurs. They’re characterized in having spiky armor,
especially on the neck and shoulders. While Allosaurus was far larger than
these potential prey, it would have significant difficulty trying to pierce
bony armor that could hurt the attacker in the meantime.

They’re each about 10 feet long, a very common size for
ankylosaurs until the middle Cretaceous Peloroplites and Sauropelta. Why did Ankylosaurs grow so small? For one
thing, most predators couldn’t harm them through the armor. It wasn’t until
early Tyrannosaurs and large dromaeosaurs evolved that large sizes became
necessary to counter their powerful weapons. For another,instead of sheer size for digestion,
ankylosaurs were very wide for extra gut for digestion. Indeed, looking at an
ankylosaur head on, they’re downright tubby.

In addition to the armor and the body shape, both Mymoorapelta
and Gargoyleosaurus had many other ankylosaurian characteristics-triangular,
slightly domed heads (longer in nodosaurs, and wide and horned for ankylosaurs),
lateral lines of armor shaped like spikes or blades, wideset, crouched legs,
and tiny herbivore teeth. These characteristics would be shared for the next
hundred million years until the extinction of the entire line at the
Creteaceous-Paleogene extinction.

Now, they are clearly not the same animals. Indeed, when
Kirkland and Carpenter and their team discovered Gargoyelosaurus, they compared
it to Mymoorapelta. Luckily, both animals were represented by good partial
skeletons so they could be compared. Gargoyleosaurus is not only an earlier
animal, but less derived as well. There’s
subtle differences in the shape of the vertebrae, scutes, pelvis, metacarpals,
caudal ribs, and skull, and the chevrons of the spine are not fused. They also
show different similarities to the other ankylosaurs.Gargoyelosaurus resembles more the true
Ankylosaurs, while Mymoorapelta has more in common with Nodosaurs. It’s
possible they were ancestors of the clades, or of the lines of Polacanthids
that later became each group. Ankylosaur evolution is still a puzzle and at the
base are these two species.

Because they’re early, small, and rare, neither species gets
much view in the public eye, being literally overshadowed by Brontosaurus,
Stegosaurus, and the rest. You can see
their specimens, however.Gargoyleosaurus is mounted underneath the Diplodocus in the Denver
Museum of Nature and Science.Mymoorapelta can be found on the other side of Colorado, in the Dinosaur
Journey Museum in Fruita. Fortunately, casts of both have been made and can be
seen in touring museums of dinosaur casts.Their relative complete specimens make them less obscure than some other
dinosaurs but they are quite obscure. And, of course, it’s their obscurity that
makes me want to promote them.

So anyway, Hollywood, give them a break. Museums, keep them
on display. Toy companies, here’s a new fresh face. Authors, think about the
crap you’re writing and how this genus could perk up the place. And remember,
shop Mymoorapelta and Gargoyleosaurus where you work or play!

I would like to thank James Kirkland for his help with the
papers for this entry. I actually wasn’t going to cover them, but I asked him a
question on these and he was gracious enough to let me read his papers on the
taxa.

About Me

Hi everyone! You may know me already, but 99% of you won't. I've decided to make a blog for myself. I'm a anthropology student who has returned to his original passion for palaeontology. Ever since I was little, I've been fascinated with the weird and wonderful animals that have inhabited our planet and I've made this blog to keep this in my mind and hopefully in yours. Most people blog about their interests, and while I've got a range of interests-see history and anthropology above, not to mention zoology, astronomy, art, cooking, science fiction and fantasy films and literature, and a myriad of others, the one I want to do for a living is the study of Earth's ancient past.

On this blog I'll review papers, talk about fossils, museums, and taxa, review art, film, literature, and our culture's view of paleontology, and share memories and insights. I've been inspired by the far better blogs of professional palaeontologists, and I'll share them as time goes on. I'm also open to requests and questions of opinions, the latest palaeo news, and discussions with other fans informal and professional.

I think this is going to have fun, and I'm hoping my readers will have just as much fun.

Copyright: All media and print reviewed belongs to the owners and publishers. Likewise, all art used for this blog belongs to their artists. This is a non-profit blog for education and entertainment.